With the approaching winter, minimum temperatures in the national capital have trended downward over the last due to the arrival of northwesterly winds called Western Disturbances.
Try this PYQ:
Q.Westerlies in the southern hemisphere is stronger and persistent than in northern hemisphere. Why?
- The southern hemisphere has less landmass as compared to the northern hemisphere.
- Coriolis force is higher in the southern hemisphere as compared to the northern hemisphere
Which of the statements given above is/are correct?
(a) Only 1
(b) Only 2
(c) Both 1 and 2
(d) Neither 1 nor 2
Western Disturbances
- A western disturbance is an extratropical storm originating in the Mediterranean region that brings sudden winter rain to the northwestern parts of the Indian subcontinent.
- It is a non-monsoonal precipitation pattern driven by the westerlies.
- The moisture in these storms usually originates over the Mediterranean Sea, the Caspian Sea and the Black Sea.
- Extratropical storms are global phenomena with moisture usually carried in the upper atmosphere, unlike their tropical counterparts where the moisture is carried in the lower atmosphere.
- In the case of the Indian subcontinent, moisture is sometimes shed as rain when the storm system encounters the Himalayas.
- Western disturbances are more frequent and strong in the winter season.
Their significance
- Western disturbances, specifically the ones in winter, bring moderate to heavy rain in low-lying areas and heavy snow to mountainous areas of the Indian Subcontinent.
- They are the cause of most winter and pre-monsoon season rainfall across northwest India.
- Precipitation during the winter season has great importance in agriculture, particularly for the rabi crops.
- Wheat among them is one of the most important crops, which helps to meet India’s food security. An average of four to five western disturbances forms during the winter season.
- The rainfall distribution and amount vary with every western disturbance.